The Empire State Building. The Burj Khalifa. One World Trade Center. The Chrysler Building. Sears Tower. These are but some of the most famous skyscrapers in the world. They tower over everything, giving cities a larger than life feel. Just looking at one of these gigantic architectural wonders makes one feel small and insignificant. Sometimes it does the opposite and makes one want to achieve big things and reach new heights. We all know they’re enormous and we all know they cost quite a bit of money to build, but let’s learn something new about skyscrapers. What defines a building as a skyscraper? Which city has the most skyscrapers? What was the world’s first skyscraper? Check out these ten interesting skyscraper facts.

To be a skyscraper, the minimum number of floors is 40. A skyscraper may also be called a high-rise, however sometimes the term skyscraper is used to describe buildings over 150 meters or 492 feet.

There are terms for buildings above 300 meters or 984 feet and 600 meters or 1,969 feet. They are Supertall and Megatall respectively.

In the late 1800’s, a building had to be at least ten storeys tall to be a skyscraper. The world’s first skyscraper, built in 1885, was the Home Insurance Building in Chicago, Illinois, which stood at 42 meters or 138 feet and was 10 storeys.

The now under construction Kingdom Tower will beat out the Burj Khalifa to become the world’s tallest skyscraper when it opens in 2020 in Saudi Arabia. It will have a height of more than one kilometer or 3,307 feet and will have cost about $1.2 billion.

Hong Kong has more skyscrapers than any other city with 308. Second place is New York City, followed by Dubai and Shanghai. Chicago and Tokyo are tied with 116 each and round out the top five.

The Empire State Building took only 410 days to build. That was over 80 years ago and it stood as the world’s tallest building for nearly 40 years. It was the first building in the world with over 100 floors. For comparison’s sake, the current tallest building in the world, the Burj Khalifa, took 2,185 days from the time construction began until completion. That’s over five times more, yet it’s only 2.17 times taller than the Empire State Building.

September 3rd was chosen to be a global commemorative day for skyscrapers, dubbed “Skyscraper Day.”September 3rd was chosen because it’s the birthday of Louis H. Sullivan, who’s known as the “father of skyscrapers.” He is believed to have designed the first ones.

The word skyscraper did not always refer to really tall buildings. Over the years the word has meant a number of different things. A couple of them include meaning a very tall man (in 1857) and a tall hat or bonnet (in 1800).

The tallest building ever envisioned was the Tokyo Tower of Babel in 1992. If it was ever built it would have housed approximately 30 million people and costed 3 quadrillion Yen.

How fast can a skyscraper be built? A 57 story skyscraper in China was built in just 19 days. The company which built the skyscraper used 2,736 modular units, and assembled them at an incredible rate of 3 floors per day.

If the general trend continues, skyscrapers will continue to get taller and taller. If originally 10 storeys made a building defined as a skyscraper, and now it’s 40 storeys, it wouldn’t be surprising if in the not too distant future 70 or even 100 storeys would be the threshold.